1. Field of the Invention
The present invention relates to a disk apparatus, and in particular to a disk apparatus which can be accessed by a plurality of host devices.
2. Description of the Related Art
With conventional disk apparatus, each host controls the disk or disk array directly, and disk security is controlled by the host device to which the disk is connected. File sharing with this type of file server client system is disclosed for example in Japanese Patent Application, First Publication No. Hei-4-58349.
A block diagram showing the configuration of a conventional disk apparatus is shown in FIG. 6. A conventional disk apparatus 201 comprises a command interpretation and execution unit 202 which interprets commands from a host device as well as executing those commands, and a data storage unit 203 in which data is stored. The command interpretation and execution unit 202, in the case of a read command for example, interprets the command, and recognizing the command as a read command directs the data storage unit 203 to read. The data storage unit 203 reads the stored data based on the read directions from the command interpretation and execution unit 202, and then transfers the data to the host device.
Common ways of connecting the host device and the disk apparatus include a SCSI (Small Computer System Interface) and Fibre Channel. Consequently, the command interpretation and execution unit 202 interprets commands from the SCSI or Fibre Channel and then outputs commands such as read and/or write, to the disk data storage unit 203.
With this type of conventional disk apparatus, usually a single host device is connected to the disk apparatus. Furthermore, even in those cases where a plurality of host devices are connected to a common disk interface, with current technology it is possible for any of the host devices to access the disk.
With advances in technology relating to the interface between the host device and the disk apparatus however, it has become feasible to connect a plurality of host devices. Using Fibre Channel, it is possible for example to use loops (FC-AL) to connect together more than 100 devices including both host devices and disk apparatus. Moreover, if switching fabric is employed the number of devices which can be connected together increases even further. Utilizing the high speed of interfaces, it is also possible to connect a plurality of host devices and disk apparatus to a single interface. With conventional disk apparatus, a problem arises that in the case where a single disk is able to be accessed by a plurality of hosts devices, access authorization can not be restricted to specific host devices.
Furthermore, with the move to large volume disk apparatus, it is possible to consider partitioning a single disk and then having each host use a different partition, but with conventional disk apparatus it has not been possible, while using a single interface, to identify a host device and then have each host device use a different partition.